1. Field of the Invention
The present invention relates to a medium provided with magnetic element, and a method and apparatus for reading information from such medium. In particular, the present invention relates to a medium that is provided with identification information indicated by at least one type of magnetic elements, and a method and apparatus for reading the identification information of the medium based on a detection result of a signal that is generated by the magnetic element when a predetermined magnetic field is applied to the magnetic element, while making it difficult to identify the identification information of the medium by visual observation.
2. Description of the Related Art
Recently, various security-enhancing methods and apparatuses have been proposed to prevent leakage of confidential or personal information and fraudulent copying or forgery of securities or other instruments.
For example, a method has been proposed for preventing forgery of securities or other instruments. According to the method, the forgery of securities or other instruments is prevented by preparing securities or other instruments on a special paper having a latent image of a specific pattern or formed with a special ink containing an infrared ray absorption agent.
In this method, if a security or other instruments prepared on the special paper is copied by a scanner (image reading apparatus) or a copier, the latent image of a specific pattern formed on the special paper with special ink is printed as a visually observable image, whereby the document thus obtained can be identified as a copied one and thus forgery can be prevented.
In addition to the above method, forgery preventing paper and securities prepared on such paper, which are extremely difficult to forge by using a color copier or the like is known. Also, an image processing apparatus and method, in which, if a specific original document is copied, a specific pattern is always added to the copy is known.
The forgery preventing paper is produced by dispersing, in a paper base made of pulp fibers, a mixture of substantially equal amounts of small pieces of paper or fiber fibrils coated with an ink containing a metameric pigment, and small pieces of paper or fiber fibrils colored with an ordinary ink of a color that appears to be the same hue as the ink containing the metameric pigment under ordinary light such as sunlight. Accordingly, when a security prepared on the forgery preventing paper is color-copied, two types of spots having different hues will appear on the copy, and thus the forgery can be prevented.
Also, an image from an original document is combined with an image from a transfer material to determine the specificity of the original document, and an output image of the original document having the specificity is always processed before being output, so that if a specific original document that is not supposed to be copied (e.g., a banknote) is copied, a trail can be obtained to find the location of the copier used for the copying.
However, according to the technology described above, the fact of copying is identified either by detecting a specific pattern which is added to a paper sheet when image information on the sheet is copied and printed out, or by adding a specific pattern to a paper sheet and detecting the same. Therefore, neither of these conventional techniques has satisfied a demand for forgery preventing paper, or a method and apparatus, which can prohibit the copying, or determine whether an original document is a specific one or not, instantaneously without scanning the paper.
Further, according to the conventional method in which a specific pattern added onto a paper sheet is detected by optically scanning the sheet, the specific pattern may be erroneously detected if a region where the pattern is formed is contaminated or stained. Therefore, there is a demand for a more reliable apparatus or method which is capable of preventing the fraudulent copying by accurately identifying non-copiable information added to a sheet without being affected by such contamination or stains.